Technical Field
The present invention relates to a wireless communication system and also relates to a method and apparatus for a network selection and traffic distribution in a heterogeneous communication environment. More particularly, the present invention relates to a method for selecting a network depending on a moving velocity at user equipment (UE) and a method for preventing a ping-pong phenomenon when the UE receives offload related message from a base station in 3GPP (The 3rd Generation Partnership Project) system, e.g., UMTS (Universal Mobile Telecommunications System), LTE (Long Term Evolution) system, etc., interworking with a wireless LAN (WLAN).
Description of Related Art
Recently wireless communication technologies have made great advances and thus communication system technologies have also evolved continuously. Among them, UMTS system is one of the 3-generation mobile communication technologies, and LTE system is getting the spotlight as the 4-generation mobile communication technology.
Additionally, the popularization of smart phones invites an exploding use of data, and mobile communication network operators are now trying to distribute users' data by combining WLAN network with the existing cellular network (i.e., 3G or 4G network) in order to cope with an explosion in data.
However, in case of blindly offloading UE staying in cellular network to WLAN network, rapid degradation in quality felt by a user may be caused. For example, if UE which is moving at a high speed passes near a WLAN access point (AP) and accesses it, the WLAN connection is cut off shortly and this causes inconvenience to a user. Further, since UE continuously discovers available WLAN in the neighborhood, a battery of UE may be consumed rapidly.
In addition, after moving to WLAN network, UE does not know a state of cellular network. Therefore, a solution for preventing UE from returning to cellular network at random is required.